Renal azotemia is a pathological condition or complication of kidney disease in which nitrogen-containing organic compounds are found in the blood in concentrations exceeding physiological norms. **Azotemia**—increased levels of nitrogenous substances (uric acid) in the blood. In healthy people, these substances are normally excreted by the kidneys. Violation of their secretion is accompanied by an increase in the concentration of nitrogenous metabolic products in the blood and occurs as both a symptom (in this case we speak of “symptomatic azotemia”) and a sign (or manifestation) of many diseases and syndromes, which allows us to consider azotemia as a secondary rather than a primary symptom . At the same time, albuminuria, significant in absolute value (more than 340 mg/day) with physiological diuresis (1.5 l/day), usually indicates the development of chronic renal failure (classical definition by J. W. Reed, P. Schlussel, 1923).